12 pound 90 watt tube amp

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plexi59

Guest
Milbert Amplifiers, Most Musical Amplifiers - has anyone seen these in the flesh? Sounds too good to be true, and the price is stiff, so I ain't buying one. I bet it has a switching power supply too (in addition to not having an output transformer). Auto-everything, put in whatever power tubes you want, adjustable power/headroom.
 
Digging some more into it, it does indeed seem like a combination of a power amp and a switching power supply. The idea is, there's a symmetrical power supply, and tubes affect the voltages in each side at lower frequencies, where the supply itself works at 250KHz+. Switching noise then gets filtered out. Speaker is connected to the output of the supply (which is zero with no signal applied). Not sure I'd call this a "tube" amp. There seem to be plenty of MOSFETs involved. Very advanced.
 
Chris Hurley said:
Bravo for trying to do something new.
Click to expand...

Heck, it's about time. Nothing much has changed in tube amplification since the 30s. It's just more gain stages and different frequency shaping between them. Probably because folks who design amps typically have no EE background of any kind. Or didn't, until now. Solid state amps are space age tech by now — 6KW in 2 rack spaces, light, high efficiency, bridge-able, can't be be fried — easy. On the tube side, forget to plug in the speaker, and chances are you will fry your output transformer, and a shorted plate can take out screen resistors (and sometimes even PCB traces) requiring actual repair.

If this works as advertised, that's some pretty badass design chops. It's not easy to design a switching supply just by itself, and they've got all sorts of complications to it. I can see why it costs so much, they've probably spent years just getting it to work well enough to sell. They also have some sort of a tech to power pedals such that you don't have to run power cables to them. I bet it's just capacitive coupling + DC on the guitar cable (sort of like how satellite antennas are powered), but still, it baffles me that no one has thought of this before. They retrofit regular pedals with it, too, it's not just their own.
 
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